Composition-irrelevant graphic measures, such as overlap \(R_{ove}\)  and alignment \(R_{ali}\)  of layout elements, are also introduced as in [1]}, [2]}. But here we exclude underlays and embellishments considering the poster nature shown in Fig. REF . Additionally, because underlays serve for other elements in posters and do not appear alone, we define a metric called underlay overlap \(R_{und}\) . For each underlay, we find all elements in other categories and intersected with it. Then we compute the overlap ratio of every element and choose the max one as \(R_{und}\) . It is positively associated with layout qualities. When \(R_{und}\)  reaches one, the underlay includes at least one other element.
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